This application claims the priority of German Application No. 100 21 132.1, filed Apr. 29, 2000, the disclosure of which is expressly incorporated by reference herein.
This invention relates to a process and a device for electronically controlling actuators of a combustion engine having variable gas exchange control via suction pipe pressure model.
Such a process and such a device for electronically controlling actuators of a combustion engine with variable gas exchange control are known particularly from German Patent document DE 43 25 902 A1. Actuators of combustion engines are, for example, a throttle valve, injection valves and at least a servomotor for cam shaft rotation and/or cam shaft switchover. An example of a cam shaft rotation and/or a cam shaft switchover for the phaseless change of the valve control time and the valve stroke is described on pages 246 and 247 of the technical book entitled xe2x80x9cAutoelektrik, Autoelektronik am Ottomotorxe2x80x9d [Autoelectrics, Autoelectronics on the Spark Ignition Engine], Bosch, VDI Publishers, 1994. The change in the valve stroke is also known by the term xe2x80x9cvariable valve drive.xe2x80x9d The change in the valve control times (especially the opening times of the inlet and/or outlet valves related to the crankshaft angle) is also known by the term xe2x80x9cvariable cam shaft adjustment.xe2x80x9d In the future, control time and valve stroke changes in combustion engines are preferably to be superposed.
In such combustion engine systems, one thing is important: either the correct calculation of the cylinder filling state as a function of the momentary suction pipe pressure, in particular for the calculation of the fuel injection volume, or the correct calculation of the suction pipe pressure needed to attain a required cylinder filling level, whose pressure is set by means of the throttle valve. In that regard, German Patent document DE 43 25 902 A1 also discloses a so-called suction pipe pressure model where the connection between the cylinder filling level and the suction pipe pressure is described by a straight line with a gradient and offset. There, the gradient and the offset are determined especially as a function of the valve overlap, that is to say, the crankshaft angle area over which an inlet valve and an outlet valve of a cylinder are opened together. This process, however, is too inaccurate, particularly in case of a superposition of the control time and valve stroke changes.
It is therefore an object of the present invention to improve upon a process or a device of the above-mentioned type with a view to the accuracy and flexibility of the control measures.
This problem is solved by providing a process and device for electronically controlling actuators of a combustion engine with variable exchange control by the use of a suction pipe pressure model, where the connection between the cylinder filling level and the suction pipe pressure is described by a straight line with a gradient and an offset. The gradient (K) and/or the offset (p0) are determined as a function of the valve overlap surface (Fxc3xc).
The invention is based on the novel realization that the suction pipe pressure model can be retained, but becomes independent of the type of gas change control when the gradient and/or the offset of the straight line that is the basis of the suction pipe pressure model is determined as a function of the valve overlap surface. The invention-based control becomes particularly accurate when one considers, in connection with the valve overlap surface, also the latter""s position, particularly with regard to a defined crankshaft angle.
On the basis of the present invention, when using the known suction pipe pressure model in spite of expanded combustion engine functions, one need not take into consideration whether a valve stroke change, a control time change or both are to be performed. Furthermore, one need not consider whether the outlet valves, the inlet valves or both types of valves are influenced. This makes for a simple but flexible system.